The invention relates to a filtration apparatus comprising in a housing filtration chamber into which there is admitted a suspension which is under pressure, the said chamber being bounded between an external surface in the form of a body of revolution and an internal surface which is nested therein and is also in the form of a body of revolution; at least one of the surfaces is formed as a filtering surface and in the case is connected to a filtrate discharge collector; at least one of the surfaces in the form of a body of revolution is capable of rotating; the annular filtration chamber is connected at one of its ends to a suspension inlet and at its other end to a product outlet.
In filtration apparatus of this kind, the suspension which is to be processed is introduced under pressure into the annular filtration chamber, the liquid component of the suspension passing through the filtration surfaces and being taken away as a filtrate by means of respective filtrate discharge collectors. The filtered product moves through the filtration chamber which is formed of coaxially arranged filtration surfaces, and is discharged therefrom by means of a product outlet. In order to obviate the formation of a solid cake layer of product on the filtration surfaces, advantageously the filtration surfaces are arranged to be capable of rotating in opposite directions to one another. As a result, shearing forces acting in the direction of revolution are produced at the surfaces, the product is kept in motion continuously and flows in a turbulent fashion towards the product outlet without forming a solid cake layer at the filtration surfaces.
But in the case of many suspensions which have to be filtered the shearing forces which can be obtained in the known filtration apparatus and the turbulence achieved in the filtration chamber are inadequate to prevent the formation of a solid cake layer on the filtration surfaces.